A dynamic random access memory or the like needs an inner circuit to increase or boost a source voltage. In order to reliably read data written into a memory cell, for example, a word line needs to be boosted. With a change of the source voltage from a low source 5 V to a low source 3.3 V, the source voltage needs to be boosted by the inner circuit. A booster circuit is used to cope with such a case. The booster circuit generates a voltage (hereinafter called a "boosted voltage") higher than the source voltage based on the source voltage.
The booster circuit must generate a boosted voltage that is stable even with a reduction in the source voltage. Further, a booster circuit for generating a stable boosted voltage using a reduced source voltage tends to be complex. A booster circuit having a simple circuit conuration would be desirable to reduce the chip area.